1. Field of the Invention
This invention relates to polyvinyl chloride compositions suited for molding and producing film which has improved melt flow and oxygen barrier properties.
2. Description of the Prior Art
Polyvinyl chloride has been widely used as a resin for many molding and coating applications. Some of the difficulties with vinyl chloride resin are associated with its high processing temperature and low thermal stability at the processing temperature. One method for increasing the melt flow of polyvinyl chloride has been to include a chain transfer agent into the polymerization reaction to reduce the molecular weight of the vinyl chloride polymer. In some cases this has been quite acceptable. Another method has been to incorporate processing acids into the polyvinyl chloride resin to improve its melt flow, thermal stability, and resistance to ultra-violet light, etc. Specific developments in the art are shown in the following patents:
U.S. Pat. No. 3,305,605, which discloses the use of cyclic carbonates having a molecular weight of from about 15,000 to 1,000,000 as a plasticizer for vinyl chloride. An example of a polycarbonate is dioxacyclohexanone.
U.S. Pat. No. 3,882,192 discloses the use of an aromatic polycarbonate in combination with an ABS graft polymer, and vinyl acetate-ethylene copolymer or styrene-maleic copolymer as a processing aid for polyvinyl chloride polymer systems. The polycarbonates were used in the polyvinyl chloride composition to improve the thermal stability of the polymer to permit processing at higher temperatures.
U.S. Pat. No. 2,807,603 discloses a vinyl chloride polymer composition having excellent physical properties including high impact strength and shock resistance. It is obtained by including a styrene-acrylonitrile copolymer as a processing aid.
U.S. Pat. No. 3,629,170 discloses a vinyl chloride polymer composition which includes an aromatic polysulfonic resin for the purpose of providing improved impact strength and thermal stability.
U.S. Pat. No. 3,760,035 discloses a vinyl chloride resin having improved impact strength and utilizes an insoluble alkyl acrylate polymer as a blending agent.